Hmm.. really? It may also depend on the particular area, not to mention movement due to school. I certainly see the growth of manga not remaining as high as it has been, but I doubt superhero GNs will catch up in the bookstore market any time soon. In ICv2’s last Bookscan report, there was only non-manga titles in the top 50:http://www.icv2.com/articles/news/7729.html
But this would be a pretty bad time for someone to try to get into the market that doesn’t really know what they’re doing. It is pretty crowded and several publishers are aligned specifically with Japanese companies, meaning top titles in Japan would be quite hard to license. Del Ray did quite well as an established publishing house breaking in, but they did everything right and even that was a ways ago.

FIRST SECOND is an imprint of Roaring Brook Press, a division of Holtzbrinck Publishers, which owns some of America's most prestigious publishers, known for great integrity and literary quality. These include Henry Holt, FSG, St Martin's Press, Tor and Picador, all of which have garnered the most coveted prizes in publishing.